Field of the Disclosure
The present disclosure relates to a machining method of machining a workpiece using a machine tool, wherein the rotational speed of a spindle of the machine tool is periodically varied.
Background of the Disclosure
It has conventionally been well known that, when a workpiece is machined using a machine tool, chatter vibration deteriorates machining accuracy (in particular, surface accuracy). Such chatter vibration is roughly classified into forced chatter vibration and self-excited chatter vibration, and it is considered that forced chatter vibration is caused by an action of an excessively large external force or by synchronization between the frequency of an external force and the resonant frequency of a vibrating system and, on the other hand, self-excited chatter vibration is caused by continuation of cutting in which periodic variation in cutting resistance and periodic variation in thickness of cut enhance each other through interaction therebetween (the so-called “regeneration effect”).
Further, conventionally, as a method of suppressing self-excited chatter vibration included in chatter vibration, a technique of periodically varying the rotational speed of a spindle at a predetermined amplitude has been suggested. Furthermore, a technique has been suggested in which the variation amplitude and the variation period of the spindle rotational speed are parameterized and the parameterized variation amplitude and variation period are changed when chatter vibration occurs.
Further, another technique has been suggested in which average rotational speed candidates having the effect of suppressing chatter vibration are determined in accordance with the following equation and a preset number of average rotational speed candidates closest to the current rotational speed are displayed on display means so that the operator can change the rotational speed to a desired one. Furthermore, the still another technique has been suggested in which the current set values are plotted on a plane whose vertical axis represents the period and whose horizontal axis represents the average rotational speed and values or ranges of the period and the average rotational speed having the effect of suppressing chatter vibration are displayed in color on the plane.R=120/(m(2n−1)N),where R is the rotational-speed variation period [s], m is the number of cutting edges of a tool, n represents an integer, and N is the average rotational speed of the spindle [min-1].